DIY Microwave Oven Transformer (MOT) Arc Welder

[SliekaStyle]

Nice. I'll wait for your videos and results about ac/dc conversion. I'm thinking..to do this with my mot welder, but i'm not sure that resulting dc will be much better than ac.Don't want to spend much money on BIG drossel(need BIG transformer core). So i'm considering the idea of turning my 3xMOT welder into three phase welder.

[Pudersepp]

@SliekaStyle

Well, I've run some simulations on LTSpice and asked around, also viewed some AC/DC welder schematics and welding tips from the millerwelds homepage. Basically, you need around 10mH, this is should be acheived with eg. 900W MOT transformer core. I'm not sure about saturation, yet. Guys with experience said that you wont feel the difference whether you choke the rectifier output or not. It is logical to an extent, since ion transfer is not reversed due to polarity flip.

[Pudersepp]

@SliekaStyle Three phases will give you better AC control I figure, I have not really looked into that. But DC gives the chanse of welding softer metals. Also, there are excellent tutorials out there, with full schematics, on how to produce a DIY MOT TIG welder. DC is the basis for this anyways. I have not welded DC in my life, but I trust what the millerwelds company says, at least for now.

[Pudersepp]

@SliekaStyle

- easier arc start, tigther weld pools and polarity control (electrode on - gives a wider pool, shallower penetration and vice versa).

[Pudersepp]

@SliekaStyle

- easier arc start, tigther weld pools and polarity control (electrode on - gives a wider pool, shallower penetration and vice versa).

[SliekaStyle]

@Pudersepp

I think that there is no way to get dc with no serious pulsating with drossel using MOT core. I'm using ltspice too. How big load do you put on output in your simulations?

I'm thinking turn welder into 3 phase, and from that get the best possible dc.

[Pudersepp]

@SliekaStyle

"I think that there is no way to get dc with no serious pulsating with drossel using MOT core"

Why do you think this?

[SliekaStyle]

I would like to see how are you welding with 3.3V under load? Can you hold arc? 

[Pudersepp]

@SliekaStyle

I can hold the arc just fine. The voltage measured here is from the "knobs", or points where the cables attach to the machine. The dry voltage is 40+ AC, meaning that when hot, the voltage is dropped elsewhere, most likely at the weld. I'll do better measurements once I finish rebuilding the unit. Going to make it AC/DC with better cooling. Will also provide a more detailed video here on youtube, since this one really says nothing informative :)

[HaikuAutomation]

@Pudersepp great stuff, look forward to hearing/viewing your results!

[Pudersepp]

@HaikuAutomation

Finished building the 4kW rectifier yesterday. Need to add a third transformer for higher voltages needed for stainless welding. In some weeks time.

[gigobait]

Why the CD-Rom in there?

[Pudersepp]

@gigobait

It is only the metal of the CD rom, it is to give magnetic shielding between the trafos and guiding the air. It guides air notably more than it shield, of course.

[mashersmasher]

i like the use of a computer case!